White quartz and lots of magnetite, making progress

[BentFunky]

Not really asking a question here as much as I'm thinking out load. However, would appreciate insight and comments from the professionals in forum.

I found a patch of really interesting ground in a stream. Was uncovered by recent flash flooding. I panned a bit of material from surface down to 6 inches or so. 2 full pans. Found notably more gold and electrum in this one spot (at the surface) then I've found elsewhere in this stream.

Sand is quartz with a large amount of magnetite. The magnetite gives ground a dark grey to black color. The quartz sand itself is translucent white. A few inches under surface, you start to see white quartz gravel and rock. No other types of rock or sand. Really homogeneous WRT variety. Rock density increases with depth. The rocks are all rounded, so likely came from somewhere else and settled there. Higher than normal concentration of gold (in this spot) could be due to the fact that gold is found in white quartz in this region.

The ground composition in this one patch is really odd. It's VERY different from immediate surroundings. Both upstream and downstream ground is composed of various clays with iron oxides, aluminosilicates, manganese, and a hodgepodge of other types of mineralization. In rest of stream, rocks are varieties of metamorphic and igneous. Good variety of stuff.

If the quartz in this one spot traveled downstream from somewhere else, I'd expect that the rest of the stream would look at least somewhat similar, but it doesn't ... now that I'm thinking about it, I might have seen similar sand on other side of stream but attributed the color to organic matter.

Given the above, seems like a plausible rationale for what I'm seeing is that there was another stream in distant past that ran almost perpendicular to this stream's current path. Evidence of this old stream could have been (mostly) eroded away by current stream's path. If so, I need to find the old waterway's "upstream" side and start looking for quartz outcropping near surface level.

Anyone ever encounter something similar?

 

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[Reed Lukens]

Depending on your location, many areas have the ancient channel maps laid out already. Finding the gold line in the ancient channel is a bit harder, but I've nailed them more then once

 

[BentFunky]

Depending on your location, many areas have the ancient channel maps laid out already. Finding the gold line in the ancient channel is a bit harder, but I've nailed them more then once

Appreciate info @Reed Lukens! I'll see if I can find channel maps. Will also take a look at topographic details. Might be able to see ancient stream paths reflected in those details. In the meantime, I can just follow the magnetite. Holy crap. There is soooo much magnetite along this path.

Took a deeper sample this am, four pans of material down to a depth of at least a foot. Would have liked to dig deeper but rock density increases with depth. Didn't have much time to work before family got out of bed.

After removing magnetite from today's dirt, l can see a little free gold and what could be significant electrum. Super fine but heavy in pan. Just a bit lighter than visible yellow gold. Dissolving sample material in AR as I type this. After dropping gold from solution, I'll have a much better idea how much is there. The gold is incredibly small around here, so it's really hard to tell what you have just by looking at pan concentrates. Fingers crossed.

Also, need to take a closer look at quartz rock mineralization.


UPDATE: Not happy with Mother Nature.
Less gold than shallower samples. Must have been silver and not electrum. I'll have to take a closer look at all the magnetite and any other ferromagnetic material from today's panning. I'm sure that at least a little gold got caught up when I was using magnet to remove that material.

Also, If I'm lucky, I'll find a clay layer if I dig a bit farther down. Given that there is gold, it's possible that I'll find it sitting below magnetite on clay layer boundary.

UPDATE to update: More gold than first believed
Additional gold settled out of solution over night, so looks like amount of gold in deeper sample is about same as first, shallower sample. Notably more than can be seen just by eye-balling concentrates.

I use aqua regia for sample testing, not processing. I'm only testing grams of material and only using acid measured in milliliters. Given this, gold concentration in test solution can be quite low. This, in turn, can give very fine precipitate that takes time to fall to bottom of container.

Additionally, a quick inspection of magnetite extracted from concentrates shows some gold as well.

Bottom line, I need to start being far more careful when preparing/extracting/measuring gold content in small test samples. Just too easy to underestimate gold content when dealing with very fine gold and small sample sizes.

Makes me wonder how many placer sites are overlooked because gold content is not obvious upon inspection of sample panning concentrates. I suppose this becomes less of a problem as sample sizes increase from a few pans to many buckets.

Can't wait to get assay results from rock samples. Probably, still have to wait another week for results. Doesn’t really meet my need for instant gratification.

 

[BentFunky]

Well, might need to rethink my emotional commitment to this site. White quartz wasn’t tested, but just received assay reports for other rocks types that looked interesting.

Best results are less than fabulous:
Gold about 1g per ton
Silver about 6g per ton
Platinum about .22g per ton
Palladium about .77g per ton

Ouch

Might get lucky and find a spot where Mother Nature concentrated gold or PGM